A Boston judge suspended Smith's 2 1/2-year sentence and placed him on five years' probation.

Smith must continue sex offender treatment, comply with Utah sex offender registry requirements and follow restrictions on contact with children and Internet use.

Prosecutors say a fellow first-class passenger saw Smith viewing pornographic computer images of young girls during a November 2011 flight. The passenger took a cellphone photo of the images and alerted a flight attendant.

Smith was arrested in Boston and initially pleaded not guilty. He resigned his job as a University of Utah engineering professor.

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